The invention relates to a method for contact-free, optical displacement- and/or vibration measurement of an object by means of at least one interferometer with at least one laser, at least one control unit which guides the laser beam to a plurality of points of the object to be measured, so that the object is scanned by the laser beam, and at least one output unit for the high-resolution display of the measurement results. The invention further relates to an apparatus for the implementation of the method.
Such a method and apparatus are known from DE 31 13 090 A1 in which the following procedure is performed: a video image of the structure to be investigated is recorded, and a rectangular grid of measurement points is inserted into this video image using a computer. In this way, a rectangular grid of measurement points is superimposed upon the object to be measured. The object to be measured is set in vibration, and the laser beam of an interferometer is directed toward the predefined grid points under the control of the computer. At each of these points the vibration spectrum is recorded in a contact-free manner by this interferometer. Following the measurement, the individual vibration spectra are analyzed in the computer, and the vibration image of the object is reconstructed for individual frequencies selected from the vibration spectrum. These vibration images are output by an output unit (image screen).
Optionally, individual measurement points can also be erased from the measurement grid.
This method and the associated apparatus are disadvantageous inasmuch as the arrangement of the measurement points in a predetermined grid is unsatisfactory for the analysis of vibrations with complicated geometric configurations. These can be recorded only by means of an extremely large number of measurement points, with the result that the measurement can no longer be performed in a reasonable period of time.
Additionally, for the analysis of vibration modes, in particular of car doors or the like, it is known to arrange individual sensors at different points of the workpiece to be measured. The sensors are accelerometers which, on the one hand, falsify the measurement result by virtue of their own bulk and, on the other hand, cannot be attached in the desired amount or at all the desired locations. Particularly in the case of small workpieces, the use of such bulky accelerometers rapidly becomes subject to insuperable limitations.